-/* Copyright (c) 2015. The SimGrid Team.
- * All rights reserved. */
+/* Copyright (c) 2015-2017. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
#define SIMGRID_MC_DWARF_EXPRESSION_HPP
#include <cstdint>
+#include <cstdlib>
-#include <stdexcept>
+#include <stdexcept> // runtime_error
+#include <utility>
+#include <vector>
+#include <elfutils/libdw.h>
+
+#include "src/mc/mc_forward.hpp"
#include "src/mc/AddressSpace.hpp"
+/** @file DwarfExpression.hpp
+ *
+ * Evaluation of DWARF location expressions.
+ */
+
namespace simgrid {
namespace dwarf {
-class evaluation_error : std::runtime_error {
-public:
- evaluation_error(const char* what): std::runtime_error(what) {}
- ~evaluation_error() noexcept(true);
-};
+/** A DWARF expression
+ *
+ * DWARF defines a simple stack-based VM for evaluating expressions
+ * (such as locations of variables, etc.): a DWARF expression is
+ * just a sequence of dwarf instructions. We currently directly use
+ * `Dwarf_Op` from `dwarf.h` for dwarf instructions.
+ */
+typedef std::vector<Dwarf_Op> DwarfExpression;
+/** Context of evaluation of a DWARF expression
+ *
+ * Some DWARF instructions need to read the CPU registers,
+ * the process memory, etc. All those informations are gathered in
+ * the evaluation context.
+ */
struct ExpressionContext {
ExpressionContext() :
cursor(nullptr), frame_base(nullptr), address_space(nullptr),
object_info(nullptr), process_index(simgrid::mc::ProcessIndexMissing) {}
-
+ /** CPU state (registers) */
unw_cursor_t* cursor;
void* frame_base;
+ /** Address space used to read memory */
simgrid::mc::AddressSpace* address_space;
simgrid::mc::ObjectInformation* object_info;
int process_index;
};
-typedef std::vector<Dwarf_Op> DwarfExpression;
+/** When an error happens in the execution of a DWARF expression */
+class evaluation_error : std::runtime_error {
+public:
+ evaluation_error(const char* what): std::runtime_error(what) {}
+ ~evaluation_error() noexcept(true);
+};
+/** A stack for evaluating a DWARF expression
+ *
+ * DWARF expressions work by manipulating a stack of integer values.
+ */
class ExpressionStack {
public:
typedef std::uintptr_t value_type;
static const std::size_t max_size = 64;
private:
- uintptr_t stack_[max_size];
+ // Values of the stack (the top is stack_[size_ - 1]):
+ uintptr_t stack_[max_size] {0};
size_t size_;
public:
ExpressionStack() : size_(0) {}
void clear() { size_ = 0; }
uintptr_t& operator[](int i) { return stack_[i]; }
uintptr_t const& operator[](int i) const { return stack_[i]; }
+
+ /** Top of the stack */
value_type& top()
{
if (size_ == 0)
throw evaluation_error("Empty stack");
return stack_[size_ - 1];
}
+
+ /** Access the i-th element from the top of the stack */
value_type& top(unsigned i)
{
if (size_ < i)
return stack_[size_ - 1 - i];
}
- // Push/pop:
+ /** Push a value on the top of the stack */
void push(value_type value)
{
if (size_ == max_size)
- throw evaluation_error("Dwarf stack overflow");
+ throw evaluation_error("DWARF stack overflow");
stack_[size_++] = value;
}
+
+ /* Pop a value from the top of the stack */
value_type pop()
{
if (size_ == 0)
- throw evaluation_error("Stack underflow");
+ throw evaluation_error("DWARF stack underflow");
return stack_[--size_];
}
- // Other operations:
+ // These are DWARF operations (DW_OP_foo):
+
+ /* Push a copy of the top-value (DW_OP_dup) */
void dup() { push(top()); }
+
+ /* Swap the two top-most values */
+ void swap() { std::swap(top(), top(1)); }
};
+/** Executes a DWARF expression
+ *
+ * @param ops DWARF expression instructions
+ * @param n number of instructions
+ * @param context evaluation context (registers, memory, etc.)
+ * @param stack DWARf stack where the operations are executed
+ */
void execute(const Dwarf_Op* ops, std::size_t n,
ExpressionContext const& context, ExpressionStack& stack);
+/** Executes/evaluates a DWARF expression
+ *
+ * @param expression DWARF expression to execute
+ * @param context evaluation context (registers, memory, etc.)
+ * @param stack DWARf stack where the operations are executed
+ */
inline
void execute(simgrid::dwarf::DwarfExpression const& expression,
ExpressionContext const& context, ExpressionStack& stack)
